Hitting the accelerator: Why SA's 74% wind power day is momentous

If you collapsed onto your couch after work last Monday (8 September 2014), and flicked on your TV, you may not have known that 10% of the power you were using came from machines that were seizing the kinetic energy stored in the movement of the atmosphere, and converting it into electricity.

For most of the day, around 10% of total power generation on the eastern seaboard’s ‘National Electricity Market’ (or NEM) came from wind farms:



It gets interesting when we drill down into a state in the NEM that has the largest installed capacity of wind farms – South Australia.

During Monday, a total of 38,973 megawatt hours of electrical energy were generated by all of the power stations in the state.  Of that, 28,957 megawatt hours came from wind farms, which was 74.3% of total power generation in South Australia, over the day.



If we look at South Australian electricity consumption instead (35,973 megawatt hours), wind power supplied 81.2% of this value. For about one and a half hours in the morning, due to low demand and high wind, the power generated by wind farms in that state met 100% of South Australian demand, with surplus power exported to Victoria:


It isn’t every day that wind power delivers three quarters of a state’s power generation, and one tenth of the entire NEM’s generation for a 24 hour period, but it’s becoming more frequent (the last time this happened was late July, this year)

Power generation from wind farms isn’t usually this high – the average level of generation for the wind energy fleet is somewhere around 30-35% of its installed capacity. Wind turbine generators need to be able to capture low winds, medium winds, and high winds.

Because wind speeds vary according the roiling mix of physics that govern the movements of the atmosphere, wind turbines need to be built like cars – they spend most of their time at average ‘speeds’, and sometimes need to reach very high ‘speeds’.

Wind conditions on Monday showed us what happens when we hit the accelerator on the Australian wind power fleet. The grid is designed such that it can handle fluctuations in wind farm power generation, very easily. AEMO forecasts wind output with high accuracy, well in advance.

There are certainly times when power generation from the wind farm fleet is low, but the frequency has decreased significantly as the number of wind farms across Australia increases:



The final words should go to AEMO, the market operator, who explain in their submission to the review of the Renewable Energy Target:

“Whilst there are technical challenges, AEMO feels the NEM design is well placed to deal with them. This includes some existing beneficial features, such as:

  • Five-minute security constrained economic dispatch and pricing.
  • The Australian Wind Energy Forecasting System (AWEFS) which is forecasting  variations in output and thereby assisting non-intermittent plant to predict dispatch.  This system is being expanded to also forecast the output of large solar plants.
  • The semi-scheduled generator provisions in the National Electricity Rules (NER) that requires intermittent generators such as wind generators to respond to AEMO dispatch signals to reduce output when network security is threatened.

The NEM has been uniquely successful in securely integrating wind generation to date at low cost. For example, AEMO has not had to change or materially increase the quantity of ancillary services purchased to maintain system security.  South Australia demonstrates the success of the NEM in integrating wind generation, given that it has one of the world’s highest wind penetrations. Wind generation there contributes 25% of total supply on average and up to 88% of local demand”

In the next post, we’ll look at the week as a whole, and dig into a comparison between a low-wind day and a high-wind day.

Access the full dataset used to create the charts and statistics here.

Access AEMO’s live-updating raw data sets of NEM  generation here.